Systems and method for manufacturing solar cell paste

ABSTRACT

Provided in one embodiment is a method of making paste for solar cells. The method can include forcing silver through a feed tube coupled to a hydrodynamic cavitation chamber using an air-driven piston. The method can include subjecting the silver to hydrodynamic cavitation in the hydrodynamic cavitation chamber by using a hydraulic pump to pass the silver sequentially through a primary orifice, a secondary orifice, and a final orifice within the hydrodynamic cavitation chamber to produce the paste for the solar cells. The silver can include up to three unique silver powders having a total particle size distribution from 0.1 microns to 10 microns. A first silver powder can have a first average particle size of 1.5 um, a second silver powder having a second average particle size of 0.5 um, and a third silver powder having a third average particle size of 0.2 um.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/749,381, filed Jun. 24, 2015, entitled “CAVITATION APPARATUS ANDMETHOD OF USING SAME,” which is a continuation of InternationalApplication No. PCT/US2013/077970, filed Dec. 27, 2013, entitled“CAVITATION APPARATUS AND METHOD OF USING SAME,” which claims priorityto U.S. Provisional applications Ser. No. 61/956,597, filed Jun. 13,2013; Ser. No. 61/848,176, filed Dec. 27, 2012; Ser. No. 61/848,177,filed Dec. 27, 2012; and Ser. No. 61/848,178, filed Dec. 27, 2012, eachof which is hereby incorporated by reference in its entirety.

BACKGROUND

Industry standard processes such as three-roll milling, attritor millingand bead milling are commonly used to fabricate dispersed particles, butthese techniques suffer several drawbacks, including poor dispersity ofthe particles and the agglomeration of the particles in the product.Emulsifying equipment that is capable of cavitating very low viscositymaterials, such as liquids, has been employed to replace the millingtechniques. However, these cavitation systems are only capable ofprocessing very low viscosity liquids; the capability of the systemconstrained by whether these materials are able to flow into themachine. These pre-existing systems are not equipped to process anymedium or high viscosity materials because these types of materialswould not be able to flow into the pre-existing cavitation systems. Forexample, in the pre-existing cavitation systems, not even yogurt mayflow into the cavitation machine.

SUMMARY

In view of the foregoing, the Inventors have recognized and appreciatedthe advantages of the systems capable of converting a raw material intofinely dispersed and non-agglomerated particles and the methods ofachieving the conversion.

Accordingly, provided in one embodiment is a method of making, themethod comprising: exposing a raw material having a first viscosity to afirst pressure and a first temperature such that the raw material afterthe exposure has a second viscosity; wherein the raw material comprisesparticles comprising at least one electrically conductive material, andwherein the second viscosity is sufficiently low for the raw material tobe adapted for a hydrodynamic cavitation process; and subjecting the rawmaterial having the second viscosity to the hydrodynamic cavitationprocess to make a product material having a third viscosity.

Provided in another embodiment is an apparatus system, comprising: afirst feed tube configured to contain a raw material, which has a firstviscosity and is to be supplied into a hydrodynamic cavitation chamberthat is downstream and separate from the apparatus system; and anair-driven piston configured to create a condition having a firstpressure and a first temperature sufficiently high to reduce the firstviscosity to a second viscosity being sufficiently low for the rawmaterial to be pushed into an orifice of the hydrodynamic cavitationchamber to undergo a hydrodynamic cavitation process to form a productmaterial.

Provided in another embodiment is a composition, comprising: particlescomprising an electrically conductive material; at least two glassmaterials; at least one organic solvent; and at least one polymermaterial. The composition may be a part of a raw material subjected to ahydrodynamic cavitation process.

Provided in another embodiment is a non-transitory computer-readablemedium, stored thereon a program, which when executed by at least oneprocessor is configured to execute a method comprising: exposing a rawmaterial having a first viscosity to a first pressure and a firsttemperature such that the raw material after the exposure has a secondviscosity, wherein the raw material comprises particles comprising atleast one electrically conductive material, and wherein the secondviscosity is sufficiently low for the raw material to be adapted for ahydrodynamic cavitation process; and subjecting the raw material havingthe second viscosity to the hydrodynamic cavitation process to make aproduct material having a third viscosity.

It should be appreciated that all combinations of the foregoing conceptsand additional concepts discussed in greater detail below (provided suchconcepts are not mutually inconsistent) are contemplated as being partof the inventive subject matter disclosed herein. In particular, allcombinations of claimed subject matter appearing at the end of thisdisclosure are contemplated as being part of the inventive subjectmatter disclosed herein. It should also be appreciated that terminologyexplicitly employed herein that also may appear in any disclosureincorporated by reference should be accorded a meaning most consistentwith the particular concepts disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled artisan will understand that the drawings primarily are forillustrative purposes and are not intended to limit the scope of theinventive subject matter described herein. The drawings are notnecessarily to scale; in some instances, various aspects of theinventive subject matter disclosed herein may be shown exaggerated orenlarged in the drawings to facilitate an understanding of differentfeatures. In the drawings, like reference characters generally refer tolike features (e.g., functionally similar and/or structurally similarelements).

FIG. 1 provides a schematic of a cavitation or emulsifying apparatussystem in one embodiment, wherein the system comprises a base machineunit that is commercially available and an apparatus system thatfacilitates feeding a raw material into the base machine unit.

FIG. 2 provides a schematic of another embodiment of an apparatus systemfurther showing the different components of the base machine unit of theapparatus system as shown in FIG. 1.

FIG. 3 provides a schematic of another embodiment of an apparatus systemfurther showing the different components of a thermal control system asan optional additional component of the apparatus system as shown inFIG. 1.

FIG. 4 provides a schematic of another embodiment of an apparatus systemfurther showing a closed, automated system comprising different valvesas an optional additional component of the apparatus system as shown inFIG. 1.

FIG. 5 provides a schematic flowchart illustrating in one embodiment afabrication process using the apparatus system described in FIG. 3.

FIG. 6 provides a schematic flowchart illustrating in one embodiment afabrication process using the apparatus system described in FIG. 4.

FIG. 7 illustrates particle size distribution for Ag particles in oneembodiment prior to a cavitation process (“starting material”) and aftera cavitation process (“cavitated”) as provided in one exemplarycavitation process.

FIG. 8A illustrates an electron microscopy (“SEM”) image of particlesprior to a cavitation process and FIG. 8B illustrates a SEM image aftera cavitation process.

DETAILED DESCRIPTION

Following below are more detailed descriptions of various conceptsrelated to, and embodiments of, an inventive system capable ofconverting a raw material into finely dispersed and non-agglomeratedparticles and the method of achieving the conversion. It should beappreciated that various concepts introduced above and discussed ingreater detail below may be implemented in any of numerous ways, as thedisclosed concepts are not limited to any particular manner ofimplementation. Examples of specific implementations and applicationsare provided primarily for illustrative purposes.

Cavitation

Cavitation may refer to the formation of vapor cavities in a liquid(e.g., small liquid-free zones such as “bubbles” or “voids”) that areformed as a result of forces acting upon the liquid. The processgenerally may occur when a liquid is subjected to rapid changes ofpressure that cause the formation of cavities where the pressure isrelatively low. When subjected to higher pressure, the voids may implodeand may generate an intense shockwave. Depending on the application, anysuitable mode of cavitation may be employed in the methods and systemsprovided herein. For example, the cavitation process in one embodimentmay involve, or be, hydrodynamic cavitation.

Hydrodynamic cavitation may refer to a process of vaporization, bubblegeneration, and bubble implosion, which occurs in a flowing liquid as aresult of a decrease and subsequent increase in pressure. Hydrodynamiccavitation may be produced by passing a liquid through a constrictedchannel at a specific velocity or by mechanical rotation of an objectthrough a liquid. In the case of the constricted channel and based onthe specific (or unique) geometry of the system, the combination ofpressure and kinetic energy may create the hydrodynamic cavitationcavern downstream of the local constriction generating high energycavitation bubbles.

Orifices and venturi may be used for generating cavitation. A venturimay be employed because of its smooth converging and diverging sections,such that that it may generate a higher velocity at the throat for agiven pressure drop across it. On the other hand, an orifice mayaccommodate more numbers of holes (larger perimeter of holes) in a givencross sectional area of the pipe. Both options are possible.

Some of the pre-existing cavitation systems utilize opposing water jetsto create the pressure needed for cavitation to occur while otherscreate the pressure and resulting vacuum by having hydraulic pumpsdriving and oscillating plungers which draw the low viscosity materialsin and then pushes the low viscosity material through the specific pointwhere cavitation occurs. However, none of these pre-existing systems isequipped to handle a raw material that has a viscosity larger than thatof a fluid, to disperse the constituents, or to attain the desiredparticle size distribution through de-agglomeration.

Cavitation Equipment

Depending on the application, any suitable equipment capable of carryingout a cavitation or an emulsifying process may be employed. Provided inone embodiment is an apparatus system, comprising: a first feed tubeadapted to contain a raw material, which has a first viscosity and is tobe supplied into a hydrodynamic cavitation chamber that is downstreamand separate from the apparatus. The system may also comprise anair-driven piston configured to create a condition having a firstpressure and a first temperature sufficiently high to reduce the firstviscosity to a second viscosity being sufficiently low for the rawmaterial to be pushed into an orifice of the hydrodynamic cavitationchamber to undergo a hydrodynamic cavitation process to form a productmaterial.

FIG. 1 provides a schematic illustration of a base cavitation oremulsifying machine 105. The machine comprises an inlet 110 and anoutlet 115. The machine may be a commercially available cavitationmachine or may be a custom-designed cavitation machine. The basecavitation machine 105 is described further below in FIG. 2. Theapparatus system provided herein configured to feed the raw materialinto the base cavitation machine 105 may refer to the system that isattached to the base cavitation machine 105, such as at the inlet 110thereof. Alternatively, the apparatus system provided herein may referto a fabrication system comprising a combination of both the basecavitation machine 105 and the attached system, as shown in FIG. 1.

Referring to FIG. 1, the apparatus system may comprise at least one feedtube 120, a raw material 125 inside the feed tube 120, and a piston 130that pushes the material down the feed tube 120, forcing it into theinlet 110 of the machine 105. The apparatus system may also comprise anair valve 135 on the back end of the feed tube 120, which air valve 135controls the flow of compressed air into the feed tube 120. Theapparatus system may comprise an air line 140, which feeds compressedair into the air valve 135 and into the feed tube 120 from a source ofcompressed air.

The base cavitation machine 105 may comprise any suitable components,depending on the application. For example, the base cavitation machinemay comprise two hydraulic pumps which are utilized to push the pastethrough a very small orifice, into a very small vacuum chamber, and outanother very small orifice that creates a specific desired backpressure. In one embodiment, this combination of small orifices with avacuum chamber in the middle is where the hydrodynamic cavitationoccurs.

Referring to FIG. 2, the base cavitation machine 105 in one embodimentmay comprise a hydraulic reservoir 225, a motor 230, which runs a pump245, to pump the hydraulic oil up to an intensifier 235, which drivesthe oscillating plunger 215 that pushes the material up into thecavitation chamber 205, while the ball check 220 closes to allow thematerial to be forced into the cavitation chamber, where the orificesare housed and the cavitation takes place. As the intensifier 235 pushesthe plunger 215 forward, hydraulic oil in the front of the intensifier235 is pushed against a nitrogen bag 240. After the plunger 215 is allthe way forward, a positioning sensor stops the hydraulic pump 245 fromdriving the intensifier 235, and the pressure accumulates against thenitrogen bag 240, causing the plunger 215 to be pushed back to itsstarting position.

Depending on the application, the setups, including the number of feedtubes, may be varied. In one embodiment, a small single feed tubecontaining the medium to high viscosity raw material may be employed forsmall batches that may be tested after each pass through the cavitationmachine. The cavitation process may generate a lot of heat in thematerial being processed. In one embodiment, a thermal control systemmay be employed to control the temperature of the product material as itexits the cavitation machine 105 so that the material may exit thecavitation process at an appropriate and stable temperature. Thetemperature is preferably below a thermal degradation temperature of theproduct material. The thermal degradation temperature is a function ofthe material properties of the constituents of the material. Forexample, downstream from the cavitation chamber, one embodiment of theapparatus system described herein may further comprise a thermal controlsystem, which comprises at least one of a heat exchanger 210, a thermalcouple, and a cooling fluid reservoir configured to supply the fluid tocool the product material discharged from the hydrodynamic cavitationchamber. The thermal control system may be configured to control thesecond temperature to be below a thermal degradation temperature of theraw material.

FIG. 3 provides a schematic illustration of the configuration of theapparatus system in one embodiment comprising a thermal control system.Referring to FIG. 3, the thermal control system may comprise a heatexchanger 305 inline directly after the material exits the cavitationprocess. The heat exchanger 305 may be followed (downstream) by athermal couple 310, which is configured to read the temperature of thematerial after the material has passed the heat exchanger 305. Chilledwater may be applied to the heat exchanger using at least a water valve315, which allows water to flow from a chilled water source 330 to theheat exchanger 305 via water tubing 320 through the heat exchanger 305,then out of the heat exchanger 305 and back to the return waterconnection of the chilled water via water tubing 325.

The flow of the water may be controlled manually or automatically, suchas by a software program. In one embodiment, a predetermined temperaturemay be inputted into a software program that, when executed, causes atleast one processor to execute the thermal control system. In anotherembodiment, the feedback from the thermal couple may enable the softwareto adjust the water valve 315 such that the temperature of the materialexiting the thermal control system is within a desired range. In oneembodiment, the material is processed in a single discrete pass anddelivered to a second tube via the outlet 115. The tubes are theninterchanged and the process may be repeated for as many passes asneeded to achieve the desired product material properties.

FIG. 4 provides a schematic illustration of an alternative embodiment ofthe apparatus system described herein. This embodiment further comprisesa closed system that allows and/or facilitates multiple cavitationpasses. The closed system, which is further downstream from the thermalcontrol system, may further comprise a second feed tube; a plurality oftwo-way valves and three-way valves configured to resupply the productmaterial back into the hydrodynamic cavitation chamber to repeat thehydrodynamic cavitation process; and a pressure transducer. Thisembodiment may be suitable for a larger-scale production than thesmaller (e.g., R&D) embodiment described above. One benefit of theclosed system described herein is mitigation (such as completeelimination) of exposure to contamination (e.g., air).

In addition to the thermal control system as shown in FIG. 3, theapparatus system as shown in FIG. 4 may additionally comprise two tubesof similar size that are set up with air driven pistons. In oneembodiment, the size of the tubes may be a factor to determine the batchsize, although there is no limit as to the amount of the material thatmay be processed by the system described herein. The automation that maybe applied to the system as described in FIG. 3 may similarly be appliedto the systems described in FIG. 4. For example, the automated systemmay use valves which control the direction of the material as it goesinto and out of the cavitation machine 105, and out of and into thefeeding apparatus system described herein. (See e.g., FIG. 1).

Referring to FIG. 4, the closed system comprises two-way valves 410A and410B, which control the direction of the material when it is beingpushed into the system, as well as the direction the material travelsafter it exits the heat exchanger 305. The system may further comprise athree way valve 415, which is desirably in sync with the two-way valves410A and 410B in order for the material to travel into the cavitationmachine 105. In one embodiment, when the material in tube 120 is forceddown the tube by the air driven piston 130, the two-way valve 410A mustbe closed so that the material travels past that valve and to thethree-way valve 415. When the material is in tube 120, the three-wayvalve 415 allows the material to travel from tube 120 into thecavitation machine 105.

After cavitation takes place, the material travels through the thermalcontrol system and out of the heat exchanger 305, and past the thermalcouple 310. At this point, the material then travels through the opentwo-way valve 410B and then into tube 405, pushing the air-driven pistondown the tube towards the back of the tube where the air valve 425supplies air to the piston in tube 405. During this process of movingthe material from tube 120 to tube 405, the air valve 425 is open sothat air is able to be pushed out of tube 405 as it fills with materialand the piston 130 is forced towards the back of tube 405. When tube 120is empty, the piston 130 inside hits the front of tube 120, and there isno more pressure on the material being forced into the machine.

A pressure transducer 420, which is located near the inlet of themachine by the three-way valve, may transmit this drop in pressure to asoftware, which then causes at least one processor to switch the two-wayvalves and three-way valves so that the material will travel from tube405 back through cavitation machine 105 and back into tube 120. Once thevalves have switched (e.g., valve 410B is closed, valve 410A is open,and valve 415 is switched) so that material travels from tube 405 intocavitation machine 105, the air valve 425 may automatically turn on andforce the piston 130 and the material down tube 405 through the entireprocess and back to tube 120.

An operator/user may choose the number of times the material will passthrough the cavitation machine, thereby repeating the cavitation and/orcooling processes (by the thermal control system). In one embodiment,after the pre-determined number of passes is achieved, the system, aswell as the air driving the valves and pistons, may automatically shutoff. This safety feature may release the air pressure once the currentcycle is completed. In one embodiment, the system setups describedherein allow samples of the material to be taken at any time todetermine if the desired results have been achieved after a certainnumber of passes at the desired operating pressure(s) andtemperature(s).

In one embodiment, the apparatus systems provided herein may control thetemperature of the material by at least one of software and severalthermal couples used to determine the temperature of the material atseveral points in the process and actuate a water valve, which controlsthe flow of chilled water to the heat exchanger put inline directlyafter the cavitation takes place. In one embodiment, the material iscooled after cavitation to reduce the temperature to a range that issuitable for the material being processed so that it remains stable andready for the next cycle or pass. Without this temperature controlsystem, the material in at least one embodiment may retain too much heatand may gain even more heat energy though each pass, resulting indamaging some of its constituents. When the material is processed withset parameters for pressure and temperature, which may be determined foreach material through trial and errors and/or parametric studies, theconsistency of the product from lot to lot is surprisingly far superiorto any other pre-existing process for preparing medium to high viscosityinks, pastes, slurries or dispersions of nano-particles. The ability tomove medium to high viscosity materials in a continuous and controlledmanner through the cavitation process by the apparatus systems andmethods described herein is unexpected over the pre-existing methods.

Fabrication Process

Provided in one embodiment is a method of making, the method comprising:exposing a raw material having a first viscosity to a first pressure anda first temperature such that the raw material after the exposure has asecond viscosity; and subjecting the raw material having the secondviscosity to the hydrodynamic cavitation process to make a productmaterial having a third viscosity. The raw material may compriseparticles comprising at least one electrically conductive material. Inone embodiment, the second viscosity may be sufficiently low for the rawmaterial to be adapted for a cavitation process, such as a hydrodynamiccavitation process.

Depending at least on the equipment involved, the method of making mayinclude a number of additional processes. For example, in the case asshown in FIG. 3, the method may further comprise cooling the productmaterial to a predetermined second temperature using a thermal controlsystem, including, for example, at least a feedback temperature control.The first temperature and the first pressure may be generated by anysuitable techniques. In one embodiment, the first pressure may begenerated by using at least an air-driven piston. Also, the firsttemperature may be generated by forcing the raw material having thefirst viscosity through at least one orifice of a hydrodynamiccavitation chamber in which the hydrodynamic cavitation process takesplace. In one embodiment, the process of forcing the material into thecavitation chamber (through the small orifice) may generate a lot ofheat. The elevated temperature as a result of the addition of this heatmay be controlled subsequently through the thermal control system asdescribed above. The driving-through-piston technique need not be theonly method to heat up the raw material (to arrive at the firsttemperature/pressure) and any other suitable methods may be used. Forexample, a heat blanket may be employed to generate the firsttemperature. Further, in some embodiments, the material may undergohydrodynamic cavitation processes multiple times. For example, themethod may further comprise comprising repeating the exposing andsubjecting steps at least once. In another embodiment, depending on thesetup, at least one of the subjecting and the exposing steps takes placein a closed system.

In some embodiments, the apparatus systems described herein allow theraw material to be preconditioned so that the raw material may be fedinto the base cavitation machine. FIG. 5 provides a flowchartillustrating in one embodiment a process of making a product materialusing a system as shown in FIG. 3. As shown in FIG. 5, the raw materialtakes the form of a multicomponent mixture that may benefit fromdispersion and de-agglomeration of the particles therein (S501). The rawmaterial is loaded into an engineered cavitation feed tube, which isattached to a cavitation system (S502). A piston in the feed tube isthen driven down the feed tube (pneumatically in this example),pushing/forcing the raw material into the cavitation machine forprocessing (S503). After the raw material is forced into the cavitationmachine, the material goes through the cavitation process and thetemperature thereof increases due at least in part to thermal energygenerated by high pressures (S504). The raw material then goes into aheat exchanger after it exits the cavitation process to cool to apredetermined temperature (or temperature range) (S505), during which athermocouple measures the temperatures downstream and/or upstream fromthe heat exchanger. A software program/system then receives feedbackfrom the thermocouple located downstream from the heat exchanger, andactuates a water valve that controls the flow of chilled water to theheat exchanger (S506). When the product exits the heat exchanger, it isat the desired predetermined temperature at least as a result of thethermal control system (S507). As a result, the product material is at astable temperature and it has been effectively de-agglomerated and allthe constituents have been dispersed from the multicomponent mixture rawmaterial (S508).

In some embodiments, the apparatus systems described herein allow theraw material to undergo the cavitation process multiple times. FIG. 6provides a flowchart illustrating in one embodiment a process of makinga product material using a system as shown in FIG. 4. As shown in FIG.6, the raw material takes the form of a multicomponent mixture that maybenefit from dispersion and de-agglomeration of particles (S601). Theraw material is loaded into an engineered cavitation feed tube, which isattached to a cavitation system (S602). A piston in the feed tube isthen driven down the feed tube (pneumatically in this example),pushing/forcing the raw material into the cavitation machine forprocessing (S603). As the mixture is pushed down feed tube 120, it goespast a closed two-way valve and travels through an open three-way valve,past a pressure transducer and thermocouple and into the cavitationmachine (S604). After the raw material is forced into the cavitationmachine, the material goes through the cavitation process and thetemperature thereof increases due at least in part to thermal energygenerated by high pressures (S605). The raw material then goes into aheat exchanger after it exits the cavitation process to cool to apredetermined temperature (or temperature range) (S606), during which athermocouple measures the temperatures downstream and/or upstream fromthe heat exchanger. A software program/system then receives feedbackfrom the thermocouple located downstream from the heat exchanger, andactuates a water valve that controls the flow of chilled water to theheat exchanger (S607). When the product exits the heat exchanger, it isat the desired predetermined temperature at least as a result of thethermal control system (S608). After the product flows out of the heatexchanger, it travels through the open two-way valve connecting to feedtube 405 and into feed tube 405, pushing the piston in feed tube 405towards the back of the tube (S609). When feed tube 120 is empty and theproduct has completed one pass, the piston that forces the product thenhits the front of the feed tube and stops; at this time the pressure ofthe product going through the three-way valve drops (S610). A pressuretransducer mounted to the three-way valve reads the pressure drop as aresult of tube 120 being empty—when the software receives this feedback,it switches the two-way valves, three-way valve, and product air valvesthat control the air pushing the piston in the feed tube (S611). Afterthe software switches the valves and air supply, the product materialbegins to feed back into the cavitation machine from feed tube 405, pasta closed two-way valve and through the three-way valve to return intothe machine (S612). The software allows a user to enter the number ofpasses and set the temperature; after this information has been enteredinto the software, the machine will run the set number of passesautomatically and with a stable temperature (S613). The product materialis at a stable temperature; it has been effectively de-agglomerated andall the constituents have been dispersed from the multicomponent mixtureraw material (S614).

The method and apparatus systems provided herein allow raw material witha higher viscosity to be subject to a cavitation process (e.g.,hydrodynamic cavitation process), in comparison to those allowed in apre-existing cavitation process. The values of the viscosities describedherein are material-dependent and thus any of the values of theviscosities discussed herein are meant only for illustration purpose andnot to be limiting. Also, the values of the viscosities may refer to thevalues measured at the particular instant of measurement during aparticular point of the process (and hence at the particular pressureand/or temperature at that particular point of time).

Because the second viscosity may be important for the raw material to bepushed into the cavitation, the fabrication methods described herein mayfurther comprise determination of the suitable first pressure and firsttemperature so as to achieve the second viscosity. The determination mayinvolve parametric studies and/or trial and errors. The determinationmay be optimized by using a certain algorithm or computer databasecontaining material properties of the different constituent materialsused in the raw material.

The first temperature and the first pressure are dependent on theprocessing conditions and material properties. In one embodiment, thefirst temperature may be between about 20° C. and about 100° C.—e.g.,between about 25° C. and about 80° C., between about 30° C. and about60° C., between about 35° C. and about 50° C., between about 40° C. andabout 50° C., etc. Other values are also possible, depending on theapplication.

In one embodiment, the first pressure may be between 100 psi and about100,000 psi—e.g., between 500 psi and about 80,000 psi, between 1,000psi and about 50,000 psi, between 2.000 psi and about 10,000 psi,between 3,000 psi and about 5,000 psi, etc. Other values are alsopossible, depending on the application.

In one embodiment of the method described herein, the first viscosity atroom temperature may be at least about 1 Kcps—e.g., at least about 5Kcps, about 10 Kcps, about 20 Kcps, about 40 Kcps, about 60 Kcps, about80 Kcps, about 100 Kcps, about 150 Kcps, about 200 Kcps, about 250 Kcps,about 300 Kcps, about 350 Kcps, about 400 Kcps, about 500 Kcps, about600 Kcps, about 700 Kcps, about 800 Kcps, about 900 Kcps, about 1000Kcps, or higher. There is no upper limit for the first viscosity. Thereis also no lower limit for the first viscosity, as the methods andsystem described herein are equipped to handle the low viscositymaterials that are processed by pre-existing cavitation techniques.

The second viscosity may generally be lower than the first viscosity dueat least in part to the process of subjecting the raw material to thefirst temperature and the first pressure. The second viscosity varieswith the material and also varies with the first pressure and the firsttemperature. For example, the second viscosity may be about 10% to about90% of the first viscosity—e.g., about 20% to about 80%, about 30% toabout 70%, about 40% to about 60%, about 45% to about 55%, etc. of thefirst viscosity. In one embodiment, the second viscosity is about 25% toabout 50% of the first viscosity.

The third viscosity (of the product material) may generally be lowerthan the first viscosity. The third viscosity varies with the materialand also varies with the processing conditions the material has beensubjected to. For example, the second viscosity may be about less thanabout 90% of the first viscosity—e.g., less than about 80%, about 75%,about 70%, about 65%, about 60%, about 55%, about 50%, about 45%, about40%, about 35%, about 30%, or less. In one embodiment, the thirdviscosity is equal to about 50% of the first viscosity. In someinstances, the third viscosity is higher than the second viscosity oncethe pressure is released and/or the temperature of the product materialis cooled.

The product material as a result of the fabrication methods describedherein may be further employed to make a variety of devices. Forexample, the method may further comprise disposing the product materialonto a substrate to form a pattern on the substrate, which substrate isa part of a device. The device may be any of the devices described in alater section. The pattern may be, for example, gridlines.

As described above, any part of the method, when used in conjunctionwith the apparatus systems described herein, may be automated. Theautomation may be accomplished at least in part using a softwareprogram. In one embodiment, the software program is stored on anon-transitory computer-readable medium. The program, when executed,causes at least one processor (such as a computer) to execute any of themethods (or portions thereof) described herein.

The methods and apparatus systems provided herein allow the size of rawmaterial to be reduced, dispersed, and/or de-agglomerated. The rawmaterial may comprise a plurality of particles. The particles may haveany geometry, including shapes and sizes. For example, the particles mayhave a shape that comprises a sphere, a sheet, a flake, a frit, anellipsoid, or an irregular shape. The particle may be of any size. Theterm “size” referred to herein may refer to the diameter, radium,length, width, height, etc., depending on the context and geometry ofthe particle. In one embodiment, when the term “size” is used todescribe a plurality of particles, the size may refer to an average sizeof the plurality.

In one embodiment, the method may comprise reducing a first size of theparticles contained in the raw material to form particles having asecond size in the product material, the second size being smaller thanthe first size. The first size may be in the nanometer range ormicrometer range. For example, the first (average) size of the particlesmay be between about 0.05 microns and about 100 microns—e.g., about 0.1microns and about 50 microns, about 0.5 microns and about 10 microns,between about 0.25 microns and about 1 micron, etc. On the other hand,the second (average) size of the particles may be between about 0.05microns and about 10 microns—e.g., about 0.1 microns and about 3microns, about 0.1 microns and about 1 micron, between about 0.25microns and about 1 micron, about 0.2 microns and about 0.5 microns,etc. The particle size reduction effect of the methods and systemsdescribed herein in one embodiment is shown in FIG. 7. As shown in FIG.7, experimental data show that the methods and systems described hereinreduce the average size of Ag particles from greater than about 20microns to about 0.2 microns. Additionally, after the process describedherein, the particles exhibit a much tighter/narrower distribution thanthose before the process.

The reduction in size may be due in part to de-agglomeration of theparticles. In other words, the method may comprise de-agglomerating theparticles having a first size contained in the raw material to formparticles having a second size in the product material, the second sizebeing smaller than the first size. FIG. 8A illustrates an electronmicroscopy (“SEM”) image of particles having a first size and containedin the raw material prior to a cavitation process. FIG. 8B illustrates aSEM image of particles having a second size and contained in the rawmaterial after a cavitation process. FIG. 8A and FIG. 8B illustrate thecontrast between particles before and after de-agglomeration as a resultof the cavitation process described herein. During de-agglomeration, theparticles may be dispersed such that no visually observableagglomeration of the particles is observed in the product material.

One surprising result of using the systems and methods described hereinto fabricate a product material comprising particles is that theparticles in the product material may remain de-agglomerated for aperiod of time. In one embodiment, the metric used to describe thephenomenon of the particles in the product material remaining at leastsubstantially de-agglomerated may be the lack of visually observablechange (e.g., increase) in the size of the particles after a period oftime. Visual observation may be carried out by naked eye, an opticalmicroscope, an electron microscope, and the like. In one embodiment, theparticles of the product material may remain at least substantially (orcompletely) free of agglomeration for at least about 1 month—e.g., atleast about 2 months, about 3 months, about 5 months, about 6 months,about 7 months, about 8 months, about 9 months, about 10 months, about11 months, about 1 year, about 1.5 years, about 2 years, about 3 years,about 4 years, about 5 years, or longer. Based on experimental dataavailable to date to the inventors, no observable agglomeration wasobserved after at least about 2 years.

Composition

The methods and systems described herein are versatile with respect tothe types of raw material they may be employed to process. Severalmaterial properties, including viscosity, geometry, size, etc., of theraw material have already been described above. The raw material mayalso comprise a plurality of different materials. In one embodiment, theraw material may comprise a composition comprising particles comprisingan electrically conductive material; at least one glass material; atleast one organic solvent; and/or at least one polymer material. In oneembodiment, the raw material comprises a composition comprising theparticles comprising silver, at least one glass material, at least oneorganic solvent, and at least one polymer material. In one embodiment,the raw material may comprise a composition comprising particlescomprising an electrically conductive material; at least two glassmaterials; at least one organic solvent; and at least one polymermaterial. Any of the constituent particles can have any of the particlesizes as described above.

Depending on the constituents of the raw material, the raw material mayhave a variety of particle sizes because each of the constituents mayhave a different particle size from the others. In some embodiments,some of the constituents have similar or the same sizes. For example,the glass material and the electrically conductive material may havesimilar or the same sizes. In some embodiments, all of the constituentshave different sizes. In one embodiment, the raw material may compriseat least two average particle size distributions—e.g., at least 3, 4, 5,6, 7, 8, or more.

The electrically conductive material may comprise any suitable materialthat is electrically conductive, depending on the application. Forexample, it may comprise a metal, an alloy, a semiconductor, and/or acarbon-based material that is electrically conductive. In oneembodiment, the electrically conductive material comprises at least oneof: Ag, Pd, Au, Pt, Ni, Cu, Ru, or an alloy thereof. A composite/mixturethereof is also possible. In another embodiment, the electricallyconductive material comprises at least one of: carbon black, graphene,carbon nanotubes, and graphite.

The glass material may comprise any type of suitable glass material,depending on the application. The glass material may comprise silicateglass. The silicate may comprise a borosilicate. The borosilicate maycomprise any type of borosilicate glass. For example, the borosilicateglass may comprise a Pb-containing borosilicate glass. Alternatively,the borosilicate glass may comprise a non-Pb-containing borosilicateglass. In one embodiment, the glass may comprise a bismuth-containingborosilicate glass. In another embodiment, the glass may comprise atellurium-containing borosilicate glass. The raw material may compriseat least two glass materials—e.g., at least 3, 4, 5, 6, 7, 8, or more.In one embodiment, the raw material comprises at least two glassmaterials, comprising: a first glass material having a first transitiontemperature; a second glass material having a second transitiontemperature, the second transition temperature being higher than thefirst transition temperature. In one embodiment, a weight ratio of thefirst glass material and the second glass material in the raw materialis 8:1. Other ratios, such as 10:1, 15:1, 20:1, etc., are also possible,depending on the application.

The glass material may have any suitable material properties, dependingon the application. For example, the glass material may have a softeningtemperature between about 300° C. and about 500° C.—e.g., between about350° C. and about 480° C., between about 400° C. and about 460° C.,between about 410° C. and about 450° C., between about 420° C. and about440° C., etc. Other softening temperature values are also possible,depending on the material.

The glass material may have a glass temperature between about 200° C.and about 500° C.—e.g., between about 250° C. and about 450° C.; betweenabout 300° C. and about 400° C.; between about 320° C. and about 385°C.; between about 340° C. and about 370° C.; between about 350° C. andabout 360° C., etc. Other glass transition temperature values are alsopossible, depending on the material.

The organic solvent may comprise any type of suitable organic solvent,depending on the application. The organic solvent may comprise at leastone of an alcohol, an aliphatic, an aromatic, a ketone, ethyl acetates,and an ester. The alcohol may comprise a monoterpene alcohol or analcohol ester. In one embodiment, the organic solvent comprises at leastone of ester alcohol and alpha terpineol. The ester alcohol may be, forexample, Texanol™.

The polymer material may comprise any type of suitable polymer material,depending on the application. The polymer material may comprise at leastone of a resin, a thixotropic agent, a lubricant, a plasticizer, and awax. The resin may comprise ethyl cellulose. The thixotropic agent maycomprise modified castor oil derivative. The lubricant or plasticizermay comprise olefin co-polymers, poly-alkyl methacrylates, styrenepolymers, etc.

In one embodiment, the raw material comprises: (i) about 3.5 to about6.0 wt. % of a glass material; (ii) about 80 to about 88 wt. % of acomposition comprising silver particles; (iii) about 10.8 to about 14.4wt. % of an organic solvent; and (iv) about 1.2 to 1.6 wt. % of apolymer material.

In one embodiment, the raw material comprises (i) about 3.5 to about 6.0wt. % of a glass material; (ii) about 65 to about 75 wt. % of acomposition comprising silver particles; (iii) about 18 to about 27 wt.% of an organic solvent; and (iv) about 2 to 3 wt. % of a polymermaterial.

In some instances, additional filler material comprisingnon-electrically conductive material may be included in the rawmaterial. In some instances, the raw material may also includeincidental, inevitable impurities. The organic solvent and/or polymermaterial may be of any suitable content of the raw material, dependingon the application. The content may change as a result of the differentprocessing the raw material has undergone. For example, the productmaterial comprises about 8-10 wt. % of at least one of (i) at least onean organic solvent and (ii) at least one polymer material. Other wt. %values are also possible.

Applications

The product material produced by the methods and systems describedherein may be employed in a variety of applications. For example, themethod may further comprise disposing the product material onto asubstrate to for an electrical connect, in the case of a raw materialcomprising an electrically conductive material. The substrate may be apart of a device selected from the group consisting of a solar cell, anelectronic device, an optoelectronic device, a printed sensor, atransparent conductive coating comprising at least one of carbonnanotubes, graphene, and indium tin oxide, advanced ceramics, abiosensor, an actuator, an energy harvesting device, a hybrid circuit, asonar, a radar, a touch screen, a 3-D printing device, and a thermalmanagement material.

Other types of applications are also possible. In one application theproduct material may be employed in Ag-filled polymer inks where lowtemperature curing is required (150° C.-250° C. range) for organic solarcell applications. In another application the product material may beemployed in Ag inks (both high temperature and polymer-based) for touchscreen applications, where fine line printing and high electricalconductivity are desirable. In one the product material may be employedin Ag or any precious or base metal electrically conductive inks/pastesfor applications, including printed sensors, transparent conductivecoatings that would be based on carbon nanotubes, graphene, indium tinoxide, etc., advanced ceramics (electrodes and termination materials),sensors including biosensors, actuators, energy harvesting devices,hybrid circuits, sonar, radar, 3-D printing, thermal managementmaterials that are both electrically and thermally conductive based onAg and/or graphene, etc.

Non-Limiting Working Example Example 1—High Temperatures Crystallinep-Type Solar Cells

This example describes an exemplary formulation for high temperaturecrystalline p-type solar cells designed to accommodate printing of veryfine gridlines (<50 um). Pre-existing typical peak firing (processing)temperatures are in the 700° C.-900° C. range. Furthermore, theformulation contains at least 3 different Ag particle sizes and shapes(ranging from nano-powders dispersed in a solvent to dry powderscommercially available) to maximize the particle packing density toachieve an increased bulk electrical conductivity over industry standardformulations in the fired state after processing. Also, pre-existinginks contain one glass composition, while the ink/paste formulationemploys multiple glass compositions with different softening points.This facilitates transporting more Ag to the emitter layer and alsoenhances the densification of the fired film through liquid phasesintering mechanisms. Denser films will have higher bulk electricalconductivities and the ability to transport more Ag to the emitter layerof the cell will result in higher efficiencies.

Based on the hydrodynamic cavitation process, with the equipmentdescribed, provided herein, solar thick film screen printableformulations (front gridline contact) with a thickness of 12-20 um andwidth of <50 microns were fabricated and listed in Table 1.

Pressures for processing the individual constituents and inks/pastesranged from 1,000 psi to 30,000 psi. The orifice diameter sizes utilizedto control the internal pressures, flow rates, particle size limitationsand cavitation levels ranged from 0.005 inches to 0.050 inches. Flowrates for the materials in the cavitation systems are dependent on andcommensurate with the various system configurations. Flow rates forsmall sample volumes were in the 100 ml per minute range whileproduction throughputs approached and even exceeded 20-30 liters perminute. The back pressure created in the cavitation region of the deviceis important and varies depending on valve designs, orifice platerestrictions, and system orientation. Temperature control of the feedmaterials and the material flowing into the system is important anddependent on the organic constituent properties. Process conditions varywith respect to the order of the addition of the various materials,respective ink/paste viscosities, process times and the % of solidmaterials in the organic medium. Yields are about 100% once the systemreached its initial charge volume that is highly beneficial whenprocessing expensive raw materials such as precious metals.

TABLE 1 Exemplary Ink Formulation Composition Range Component (wt. %)Glass frit particles 3.5-6.0 Silver particles 80-88 Solvents 10.8-14.4Polymer Constituents 1.2-1.6

The temperature for processing the Ag solar front-side paste asdescribed in Table 1 was about 38° C. to 48° C. The pressure range forprocessing was about 4,500 psi-45,000 psi. With respect to the orificesizes of the cavitation machine, three different orifice sizes insequence were used to create the pressure transitions need to form avacuum and then cause the vacuum bubbles to implode. A primary orifice,then several secondary orifices, then a final orifice were used tocreate backpressure. The primary 0.020″ orifice was used to break uplarger agglomerates. After 3 passes, it was switched to primary orifice0.015″, secondary orifices 0.068″, final orifice to create back pressure0.038″ all in sequences. This Example employed 12 passes (3 passes withprimary 0.020″, then remaining 9 with primary orifice 0.015″).

The Ag average particle sizes were in the range of <0.1 microns to 3.0microns. The range for the total particle size distribution was from 0.1microns to 10 microns. Three different Ag powders spherical in naturewere used to optimize packing density. The average particle sizes of thethree various spherical powders were 0.2 um, 0.5 um, and 1.5 um. Theratio of each on a wt. % basis in the solar composition in this Examplen is as follows: 4:2:94 (based on 87% total Ag weight in the solar inkformulation). The weight ratios vary depending on the solar gridlinewidth requirements. The primary larger constituent remains the primarycomponent for Ag spheres and was >80% while the smaller sizes may eachrange from 0-15 wt. %.

Borosilicate glasses comprising silicon-boron-lead-aluminum (that mayhave a substitute such as bismuth for lead) were utilized in theink/paste formulations described in this Example. The glass compositionfor this Example is 4.5 wt. % and is based on 2 different glasscompositions that have properties in the ranges specified above. Thehigher temperature melting glass is typically the major constituent witha ratio of 8:1 for the 2-glass mixture. The lower temperature meltingglass composition assists in the liquid phase sintering of the Agparticles and uniform etching through the antireflective coating layerto make contact at the emitter layer where the charge carriers reside.

The organic solvent and polymer constituents are in the wt. % rangeshown in Table 1. Solvents are Texanol™ and alpha terpineol in an 8:1ratio, while the polymer constituents may vary based on the gridlinegeometry requirements. Typical polymer constituents include ethylcelluloses, thixotropic agents, plasticizers and waxes. The % of organicvehicle (in the ink/paste formulation) which is synthesized from thesolvents and various polymers into the single carrier composition is inthe 8-10 wt. %.

Example 2—Low Temperature Ag Inks for Solar Cells

Silver (Ag) conductive ink/paste formulations in this Example weredeveloped for the next generation of solar cell designs, such as theback passivated solar cells. The designs described in this Exampleutilize cell construction configurations that will increase the longwavelength carrier collection due to improved back side reflectance(BSR) and reduced back surface recombination velocity (BSRV). The lowBSRV and high BSR will lead to higher solar cell efficiencies. Incontrast to the requirements of typical front Ag gridlines onpre-existing solar cells in production, the Ag inks described in thisexample adhere strongly to back side dielectric after sintering at lowtemperature (250° C.-450° C.) to give very high conductivity (<2micro-ohm·cm) and preserve the passivation property of the back sidedielectric.

These Ag inks contain a glass constituent that has low softening andmelting points, as well as a low glass transition temperature. Theseglass powders soften, melt, and flow in order to provide liquid-phaseassisted sintering at temperatures at or below 450° C. with an optimummaximum below 400° C. In contrast, Ag inks for pre-existing front-sidegridlines are designed for processing above 700° C.

The Ag film formed in this Example have the following characteristics:The Ag and glass powders and/or flakes have a fine and narrow particlesize distribution in order to achieve densification and acceptableelectrical conductivity at such a low cell processing temperature. TheAg film forms an acceptable electrical contact to the rear contacts thatare typically Ag/Al or Ag pads or vias. The Ag film does not penetratethe passivation layer to any extent but must have good adhesion to same.The Ag film is able to be deposited by screen-printing or an alternativedeposition method. If the electrical conductivity is high enough, thefilm thickness is minimized, thus saving significant materials costs.The composition of the Ag screen-printable formulation for such designsdescribed in this Example is shown in Table 2.

TABLE 2 Exemplary Ink Formulation Preferred Composition Range Component(wt. %) Glass frit particles 3.5-6.0 Silver particles 65-75 Solvents18-27 Polymer Constituents 2.0-3.0

The temperature for processing the Ag solar front-side paste asdescribed in Table 1 was about 30° C. to 45° C. The pressure range forprocessing was about 1,000 psi-20,000 psi. With respect to the orificesizes of the cavitation machine, three different orifice sizes insequence were used to create the pressure transitions need to form avacuum and then cause the vacuum bubbles to implode. A primary orifice,then several secondary orifices, then a final orifice were used tocreate backpressure. The primary 0.020″ orifice was used to break uplarger agglomerates. After 3 passes, it was switched to primary orifice0.015″, secondary orifices 0.068″, final orifice to create back pressure0.038″ all in sequences.

Borosilicate glasses comprising silicon-boron-lead-aluminum (that mayhave a substitute such as bismuth for lead) were utilized in theink/paste formulations described in this Example. The glass compositionshave softening points in the range of 330° C. to 350° C. The glasstransition temperature range is from 250° C.-270° C. The particle sizeranges for the glass and Ag flakes and spheres are the same as describedin Example 1.

ADDITIONAL NOTES

All literature and similar material cited in this application,including, but not limited to, patents, patent applications, articles,books, treatises, and web pages, regardless of the format of suchliterature and similar materials, are expressly incorporated byreference in their entirety. In the event that one or more of theincorporated literature and similar materials differs from orcontradicts this application, including but not limited to definedterms, term usage, described techniques, or the like, this applicationcontrols.

While the present teachings have been described in conjunction withvarious embodiments and examples, it is not intended that the presentteachings be limited to such embodiments or examples. On the contrary,the present teachings encompass various alternatives, modifications, andequivalents, as will be appreciated by those of skill in the art.

While various inventive embodiments have been described and illustratedherein, those of ordinary skill in the art will readily envision avariety of other means and/or structures for performing the functionand/or obtaining the results and/or one or more of the advantagesdescribed herein, and each of such variations and/or modifications isdeemed to be within the scope of the inventive embodiments describedherein. More generally, those skilled in the art will readily appreciatethat all parameters, dimensions, materials, and configurations describedherein are meant to be exemplary and that the actual parameters,dimensions, materials, and/or configurations will depend upon thespecific application or applications for which the inventive teachingsis/are used. Those skilled in the art will recognize many equivalents tothe specific inventive embodiments described herein. It is, therefore,to be understood that the foregoing embodiments are presented by way ofexample only and that, within the scope of the appended claims andequivalents thereto, inventive embodiments may be practiced otherwisethan as specifically described and claimed. Inventive embodiments of thepresent disclosure are directed to each individual feature, system,article, material, kit, and/or method described herein. In addition, anycombination of two or more such features, systems, articles, materials,kits, and/or methods, if such features, systems, articles, materials,kits, and/or methods are not mutually inconsistent, is included withinthe inventive scope of the present disclosure.

The above-described embodiments of the invention may be implemented inany of numerous ways. For example, some embodiments may be implementedusing hardware, software or a combination thereof. When any aspect of anembodiment is implemented at least in part in software, the softwarecode may be executed on any suitable processor or collection ofprocessors, whether provided in a single computer or distributed amongmultiple computers.

In this respect, various aspects of the invention may be embodied atleast in part as a computer readable storage medium (or multiplecomputer readable storage media) (e.g., a computer memory, one or morefloppy discs, compact discs, optical discs, magnetic tapes, flashmemories, circuit configurations in Field Programmable Gate Arrays orother semiconductor devices, or other tangible computer storage mediumor non-transitory medium) encoded with one or more programs that, whenexecuted on one or more computers or other processors, perform methodsthat implement the various embodiments of the technology discussedabove. The computer readable medium or media may be transportable, suchthat the program or programs stored thereon may be loaded onto one ormore different computers or other processors to implement variousaspects of the present technology as discussed above.

The terms “program” or “software” are used herein in a generic sense torefer to any type of computer code or set of computer-executableinstructions that may be employed to program a computer or otherprocessor to implement various aspects of the present technology asdiscussed above. Additionally, it should be appreciated that accordingto one aspect of this embodiment, one or more computer programs thatwhen executed perform methods of the present technology need not resideon a single computer or processor, but may be distributed in a modularfashion amongst a number of different computers or processors toimplement various aspects of the present technology.

Computer-executable instructions may be in many forms, such as programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

Also, the technology described herein may be embodied as a method, ofwhich at least one example has been provided. The acts performed as partof the method may be ordered in any suitable way. Accordingly,embodiments may be constructed in which acts are performed in an orderdifferent than illustrated, which may include performing some actssimultaneously, even though shown as sequential acts in illustrativeembodiments.

All definitions, as defined and used herein, should be understood tocontrol over dictionary definitions, definitions in documentsincorporated by reference, and/or ordinary meanings of the definedterms.

The indefinite articles “a” and “an,” as used herein in thespecification and in the claims, unless clearly indicated to thecontrary, should be understood to mean “at least one.” Any ranges citedherein are inclusive.

The terms “substantially” and “about” used throughout this Specificationare used to describe and account for small fluctuations. For example,they may refer to less than or equal to ±5%, such as less than or equalto ±2%, such as less than or equal to ±1%, such as less than or equal to±0.5%, such as less than or equal to ±0.2%, such as less than or equalto ±0.1%, such as less than or equal to ±0.05%.

The phrase “and/or,” as used herein in the specification and in theclaims, should be understood to mean “either or both” of the elements soconjoined, i.e., elements that are conjunctively present in some casesand disjunctively present in other cases. Multiple elements listed with“and/or” should be construed in the same fashion, i.e., “one or more” ofthe elements so conjoined. Other elements may optionally be presentother than the elements specifically identified by the “and/or” clause,whether related or unrelated to those elements specifically identified.Thus, as a non-limiting example, a reference to “A and/or B”, when usedin conjunction with open-ended language such as “comprising” may refer,in one embodiment, to A only (optionally including elements other thanB); in another embodiment, to B only (optionally including elementsother than A); in yet another embodiment, to both A and B (optionallyincluding other elements); etc.

As used herein in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of” or “exactly one of,” or, when usedin the claims, “consisting of,” will refer to the inclusion of exactlyone element of a number or list of elements. In general, the term “or”as used herein shall only be interpreted as indicating exclusivealternatives (i.e. “one or the other but not both”) when preceded byterms of exclusivity, such as “either,” “one of,” “only one of,” or“exactly one of” “Consisting essentially of,” when used in the claims,shall have its ordinary meaning as used in the field of patent law.

As used herein in the specification and in the claims, the phrase “atleast one,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) mayrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

In the claims, as well as in the specification above, all transitionalphrases such as “comprising,” “including,” “carrying,” “having,”“containing,” “involving,” “holding,” “composed of,” and the like are tobe understood to be open-ended, i.e., to mean including but not limitedto. Only the transitional phrases “consisting of” and “consistingessentially of” shall be closed or semi-closed transitional phrases,respectively, as set forth in the United States Patent Office Manual ofPatent Examining Procedures, Section 2111.03.

The claims should not be read as limited to the described order orelements unless stated to that effect. It should be understood thatvarious changes in form and detail may be made by one of ordinary skillin the art without departing from the spirit and scope of the appendedclaims. All embodiments that come within the spirit and scope of thefollowing claims and equivalents thereto are claimed

What is claimed:
 1. A solar cell paste manufactured according to amethod comprising: providing an electrically conductive material;forcing the electrically conductive material through an orifice of ahydrodynamic cavitation chamber; and subjecting the electricallyconductive material in the hydrodynamic cavitation chamber to ahydrodynamic cavitation process by passing the electrically conductivematerial sequentially through a primary orifice, a secondary orifice,and a final orifice within the hydrodynamic cavitation chamber to make acomposition.
 2. The method of claim 1, wherein providing comprisesproviding the electrically conductive material that includes at leastone glass material.
 3. The method of claim 1, wherein providingcomprises providing the electrically conductive material that comprisesat least one of Ag, Pd, Au, Pt, Ni, Cu, Ru, or an alloy thereof.
 4. Themethod of claim 1, wherein providing comprises providing theelectrically conductive material that comprises at least one of carbonblack, graphene, carbon nanotubes, and graphite.
 5. The method of claim1, wherein forcing comprises forcing the electrically conductivematerial through the orifice of the hydrodynamic cavitation chamber suchthat a viscosity of the composition is lower than the electricallyconductive material.
 6. The method of claim 1, wherein subjectingcomprises subjecting the electrically conductive material having a firstviscosity to the hydrodynamic cavitation process in the hydrodynamiccavitation chamber by passing the electrically conductive materialsequentially through the primary orifice, the secondary orifice, and thefinal orifice within the hydrodynamic cavitation chamber to make thecomposition having a second viscosity that is lower than the firstviscosity.
 7. The method of claim 1, wherein subjecting comprisessubjecting the electrically conductive material having a first viscosityto the hydrodynamic cavitation process in the hydrodynamic cavitationchamber by passing the electrically conductive material sequentiallythrough the primary orifice, the secondary orifice, and the finalorifice within the hydrodynamic cavitation chamber to make thecomposition having a second viscosity that is higher than the firstviscosity.
 8. The method of claim 1, wherein subjecting furthercomprises: heating the electrically conductive material to a temperaturebetween 38° C. and 48° C.; and pressurizing the electrically conductivematerial to a pressure between 4,500 pounds per square inch (PSI) and45,000 PSI.
 9. A composition for solar cell paste having a viscosity ofat least 1 Kcps at 25° C., comprising: an organic solvent; a polymermaterial; and particles comprising an electrically conductive materialdispersed throughout the composition, the composition having aconductivity less than 2 micro-ohm·cm and a sintering temperature lessthan 450 C.
 10. The composition of claim 9, wherein the electricallyconductive material comprises at least one of Ag, Pd, Au, Pt, Ni, Cu,Ru, or an alloy thereof.
 11. The composition of claim 9, wherein theelectrically conductive material comprises at least one of carbon black,graphene, carbon nanotubes, and graphite.
 12. The composition of claim9, wherein the organic solvent comprises at least one of ester alcoholand alpha terpineol.
 13. The composition of claim 9, wherein the polymermaterial comprises at least one of a resin, a thixotropic agent, alubricant, a plasticizer, and a wax.
 14. The composition of claim 9,wherein the composition comprises a first glass material.
 15. Thecomposition of claim 14, wherein the first glass material comprisesborosilicate.
 16. The composition of claim 14, wherein the first glassmaterial has at least one of the following: a softening temperaturebetween 400° C. and 460° C.; a glass transition temperature between 320°C. and 385° C.; and an average particle size between 0.1 microns and 3microns.
 17. The composition of claim 14, wherein the compositioncomprises: 3.5 to 6.0 wt. % of the first glass material; 80 to 88 wt. %of the particles comprising the electrically conductive material; 10.8to 14.4 wt. % of the organic solvent; and 1.2 to 1.6 wt. % of thepolymer material.
 18. The composition of claim 14, wherein thecomposition comprises: 3.5 to 6.0 wt. % of the first glass material; 65to 75 wt. % of the particles comprising the electrically conductivematerial; 18 to 27 wt. % of the organic solvent; and 2 to 3 wt. % of thepolymer material.
 19. The composition of claim 14, wherein thecomposition comprises a second glass material that is different from thefirst glass material.
 20. The composition of claim 19, wherein the firstglass material has a first transition temperature, wherein the secondglass material has a second transition temperature higher than the firsttransition temperature, and wherein a weight ratio of the first glassmaterial and the second glass material in the composition is 8:1.